Corosync (project)

Corosync Cluster Engine

Developer(s)	The Corosync Development Community
Written in	C
Operating system	Cross-platform
Type	Group Communication System
License	New BSD License
Website	http://www.corosync.org/

The Corosync Cluster Engine is an open source project Licensed under the New BSD License derived from the OpenAIS project. Corosync's mission is to develop, release, and support a community defined de-facto open source cluster executive for use by multiple open source and commercial cluster projects or products.

Features

The Corosync Cluster Engine is a group communication system with additional features for implementing high availability within applications.

The project provides four C programming interfaces features:

• A closed process group communication model with virtual synchrony guarantees for creating replicated state machines.
• A simple availability manager that restarts the application process when it has failed.
• A configuration and statistics in-memory database that provide the ability to set, retrieve, and receive change notifications of information.
• A quorum system that notifies applications when quorum is achieved or lost.

The software is designed to operate on UDP/IP and InfiniBand networks natively.

Architecture

The software is composed of an executive binary which uses a client-server communication model between libraries and service engines. Loadable modules, called service engines, are loaded into the Corosync Cluster Engine and use the services provided by the Corosync Service Engine internal API.

The services provided by the Corosync Service Engine internal API are:

• An implementation of the Totem Single Ring Ordering and Membership^[1] protocol providing the Extended Virtual Synchrony model^[2] for messaging and membership.
• The coroipc high performance shared memory IPC system.^[3]
• An object database that implements the in memory database model.
• Systems to route IPC and Totem messages to the correct service engine.

Additionally Corosync provides several default service engines that are used via C Application Programming Interfaces:

• cpg - Closed Process Group
• sam - Simple Availability Manager
• confdb - Configuration and Statistics database
• quorum - Provides notifications of gain or loss of quorum

History

The project was formally announced in July 2008 via a conference paper at the Ottawa Linux Symposium.^[4] The source code of OpenAIS was refactored such that the core infrastructure components were placed into Corosync and the SA Forum APIs were kept in OpenAIS.

References

1. ^ Amir, Y.; Moser, L.E.; Melliar-Smith, P.M.; Agarwal, D.A.; Ciarfella (November 1995). The Totem Single Ring Ordering and Membership Protocol. 13. pp. 311–342. 
2. ^ Moser, L.E.; Amir, Y.; Melliar-Smith, P.M.; Agarwal, D.A. (November 1995). "Extended Virtual Synchrony". ACM Transactions on Computer Systems 13 (4): 311–342.  Also in Proceedings of DCS, pp. 56-65, 1994.
3. ^ Dake, S. (July 2009). Proceedings of the Linux Symposium. pp. 61–68. 
4. ^ Dake, S.; Caulfield, C.; Beekhof, A. (July 2008). "The Corosync Cluster Engine". Proceedings of the Linux Symposium: 85–99. 

External links

• Corosync Cluster Engine project
• OpenAIS project